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MAA (ANDE-MAA, NO 61, Navy-OSCAR 61)

The Atmospheric Neutral Density Experiment (ANDE) Risk Reduction Mission consists of two spherical spacecraft fitted with retro-reflectors for satellite laser ranging (SLR). Two ANDE missions, each with two satellites, were launched from the Space Shuttle in 2006 and 2008 respectively.

This experiment consisted of two micro satellites, the Mock ANDE Active (MAA) spacecraft
and the Fence Calibration (FCal) spacecraft, that were launched from the Space Shuttle cargo bay.

The main mission objective of the first mission (ANDE RRM) was to test the deployment
mechanism from the shuttle for the ANDE flight in 2008 and to begin preliminary scientific
measurements. Scientific objectives of the ANDE missions include monitoring total neutral
density along the orbit for improved orbit determination of space objects, monitoring the
spin rate and orientation of the spacecraft to better understand in-orbit dynamics, and to
provide a test object for polarimetry studies. The mission provided objects in low
Earth orbit with well-determined ballistic coefficients and radar cross-sections for
comprehensive atmospheric modeling. Each mission included a passive and an active
spherical spacecraft in a lead-trail orbit configuration. The passive sphere will be
tracked with the Space Surveillance Network (SSN) and SLR to study atmospheric drag and
in-track total density. The active sphere had on-board instrumentation to measure
atmospheric density and composition. The active sphere monitored its position relative
to the passive sphere to study drag models. The active satellite communicated
on-board data through a system of modulated retro-reflectors (MRR).

The MAA (Mock ANDE Active) spherical 50 kg satellite was 19 inches in
diameter and constructed from two anodized aluminum hemispheres. The hemispheres were
formed by spin-casting aluminum. They were then rough machined, heat treated, machine
finished, and finally, anodized. The equator of this sphere was constructed from an
engineered polymer material that is a durable, lightweight, low-wear, low-friction plastic
that acts as a non-conductive separator between the hemispheres. This allows the
satellite's shell to perform as a dipole antenna for the communications system developed
at the U.S. Naval Academy. The communications system is powered by four battery boxes,
which gives the satellite an estimated lifetime of about 1.5 years. The payload is split
into the two hemispheres, with two battery banks, a communications box, and the laser
driver box stacked in a vertical configuration.

The MAA sphere is painted with a pattern of four 90¼ longitudinal segments,
alternating bare black anodized aluminum and gloss white paint. The purpose of this paint
scheme is two-fold; to provide an easy visual pattern for observing the initial spin rate
and orientation, and to provide means to determine spin rate and orientation from the
polarization return to be observed from the Air Force Maui Optical and Supercomputing
(AMOS) facility.

Onboard instrumentation for the MAA satellite consists of a set of six CIGS
photovoltaic cells that are mounted flush with the surface of the sphere. These light
sensors are located at the endpoints of three nearly orthogonal axes and are used for
attitude and spin rate determination. Thermistors (thermally-sensitive resistors whose
resistance changes with temperature) are placed at several points within the satellite to
monitor the temperature of the various components of the satellite. The temperature and
photovoltaic voltage values are telemetered to the ground by a "heartbeat"
communications system that activates for 2 seconds out of every 20 seconds. If a ground
station is detected, the data are transmitted; if not, the system returns to a sleep cycle
for another 20 seconds. A set of six laser diodes, also located at the endpoints of three
nearly orthogonal axes, are programmed to turn "on" during passes over Maui.
These diodes emit light at 810 nanometers (nm), which will be observed from the AMOS
facility.

The Naval Academy has been given the opportunity to construct a digital communications
transponder for use in the Amateur Satellite Service to fit inside the ANDE sphere similar
to what it is flying on the PCSat 1 and PCSat 2 missions. The
PCSat-like follow-on packet communications mission will continue the interest of students
worldwide by letting them communicate via the satellite and capture telemetry relative to
its temperature in the space environment.

ANDE-MAA failed to deploy after it became stuck in its launch canister, but did finally
deploy on 22.12.2006 and has been observed by NORAD.